George Francis FitzGerald
Millenium Discourse by J. M. D. Coey
Scientific Background and Achievements
To gain some impression of the intellectual and social environment in which FitzGerald was working in the last quarter of the 19th century, and to gauge his achievement, we must understand that this was the time of the electromagnetic revolution when human life was being irrevocably transformed by the ability to deliver energy and transfer information at the flick of a switch. The tyranny of dawn and dusk, barely mitigated by 2 watt candles and gaslight was shattered by Edison's incandescent bulbs. Telegraph cables spanned continents and crossed the ocean floors conveying intercontinental chatter for a shilling a word at the speed of light . Electric tramways were introduced from the Giant's Causeway to the streets of Belfast and Dublin. Industry used electric furnaces, electric motors and electrolytic plating vats. X-rays, demonstrated at church fairs, were making their way into hospitals for medical diagnosis. In FitzGerald's memorable words,
"We are harnessing the all-prevading ether to the chariot of human progress and using the thunderbolt of Jove to advance the material progress of mankind."
And he was in no doubt that the achievement of the 19th century
"Enabling rich and poor to lead better lives by making life less hard and grimy ... improved the well-being of man both materially and, what is far more important, morally as well,"
was a direct result of scientific discoveries, invention and theories. This link between pure science and practical engineering was then quite new. Bitingly dismissive of an English authority fond of poking fun at professors to whom he thought the progress of telegraphy and telephony owed nothing, FitzGerald rises to the defence of the abstract scientific man:
"I do know that telegraphy owes a great deal to Euclid and other pure geometers, to the Greek and Arabian mathematicians who invented our scale of numeration and algebra, to Galilleo and Newton who founded dynamics, to Newton and Leibnitz who invented the calculus, to Volta who discovered the galvanic cell, to Oersted who discovered the magnetic action of currents, to Ampère who found the laws of their action, to Ohm who discovered the law of resistance of wires, to Wheatstone, to Faraday, to Lord Kelvin, to Clerk Maxwell, to Hertz. Without the discoveries, inventions and theories of these abstract scientific men there would have been no advance on the previous method of telegraphy by irritating snails."
According to FitzGerald, no distinction is to be made between the teachings of "actual experience" and "laboratory research", because laboratory research is actual experience, albeit on a small scale.
The unifying framework behind all of 19th century electromagnetism was Maxwell's theory, of which Richard Feynmann remarked that "from the long view of the history of mankind 10,000 years from now, there can be little doubt that the most significant event in the 19th century will be seen as Maxwell's discovery of the laws of electrodynamics" ; not Napoleon, not Marx, not Freud, not the abolition of slavery and serfdom, not the convulsions of the Commune, the Indian mutiny or the American civil war, but the mathematical physics of James Clerk Maxwell.
Today we think of Maxwell's theory in terms of four famous equations relating the electric and magnetic fields with the electric and magnetic fluxes, plus the Lorentz expression for the force on a moving charge. But this is not what Maxwell left us in his rambling and often obscure two-volume Treatise on Electricity and Magnetism. The chapter entitiled "General Equations of the Electromagnetic Field" includes no fewer than 13 of them labelled A to L, given in both cartesian coordinates and in Hamilton's quaternion notation. The general equations involve both the fields and the scalar and vector potentials f and A. Furthermore the physical sense of the equations was considered to be a complex system of strains and vortex motions in the ether, that tenuous but all-prevading medium through which light and every other electromagnetic disturbance was believed to propagate. The necessity of the ether was self-evident, at least to British savants at the time. FitzGerald liked to pose the rhetorical question "What becomes of light during the eight minutes it takes to travel from the Sun to Earth?" The answer was some stretching and swirling of the medium required for propagating the transversely-polarized waves that Fresnel had shown light to be; an Aristotelian link between the mover and the moved. The detailed structure of the ether was a subject for lively speculation. It was likened to a "thin jelly" or a "vortex sponge", but not to any normal fluid because it had to be able to sustain transverse modes. Models were built and their merits debated at the regular meetings of the British Association or in the columns of Nature or the Philosophical Magazine. The ether provided Maxwell and his followers with a peg for their physical imagination and a sensual appreciation of the real content of the equations. His electrodynamics, more latent than patent in his Treatise, were worked out, corrected and presented to the world in digestible and useful form after his death from cancer at 48 in 1879 by a group of followers known to historians of science, following Bruce Hunt, as the "Maxwellians" - Oliver Lodge, Oliver Heaviside, Heinrich Hertz, Joseph Larmor and George Francis FitzGerald. Of these, arguably the most influential was FitzGerald.
FitzGerald never actually met Maxwell, or corresponded with him directly. Their closest contact came after FitzGerald submitted his first important paper to the Royal Society and received from secretary George Gabriel Stokes a referee's report written by Maxwell It arrived just two days after Maxwell had died. The report contains detailed criticisms of the work, and a plea to justify the physical basis of his equations. Stokes comments, quite wrongly as regards FitzGerald,
"The physical bent of Maxwell's mind would naturally lead him to picture himself a physical state, and then set himself to work out the mathematics of it. The bent of your mind is rather to look at the mathematical expressions and then seek for the physical interpretations, or perhaps even in great measure leave that alone."
In fact FitzGerald always had a keen physical sense, and it is only because of his familiarity with the Dublin school of mathematics and physics that he launches directly into the formalism. Bartholemew Lloyd had made Dublin a significant mathematical centre in the first third of the century, and the tradition was developed by W. R. Hamilton, James McCullagh, George Salmon, Samuel Haughton and J H Jellett (FitzGerald's father-in-law). McCullagh was a brilliant young teacher who did much to promote the marriage of geometric and analytic methods which characterized the Dublin school. His achievements in optics, notably the idea of rotational elasticity of the ether as a means of explaining all of physical optics, were celebrated in College long after his suicide in 1847. His papers were regarded as classics. FitzGerald studied them closely while preparing for the fellowship examination and it was in seeking to give a new interpretation to McCullagh's formalism that he turned to Maxwell's field theory, extending the electromagnetic theory to the reflection and refraction of light, including the Kerr effet. This had eluded Maxwell himself, and it marked a spectacular debut for FitzGerald in the Proceedings of the Royal Society,
FitzGerald had a direct link back to McCullagh in the person of his uncle, George Johnstone Stoney FRS, who corresponded prolifically with his nephew throughout his career. Stoney, a physicist who is now remembered only for having named the electron, also influenced FitzGerald philosophically. Like Berkley, he regarded the world of phenomena, and the motion of the elemental ether in particular, as a manifestation of the thought of God. The electron was first conceived of by Stoney as an ethereal singularity rather than a charged point particle.
To deepen their understanding and get ideas about the workings of the ether, the Maxwellians turned to their models. These were real or imaginary mechanical models with tiny wheels and pumps, paddles and canals. FitzGerald's friend in Liverpool Olivier Lodge had come up with one based on ratchets and cogs. FitzGerald had a better idea, an array of brass wheels mounted in a large array on a mahogany base was connected by indiarubber bands which were strained as the wheels turned. The object was to visualise the flow of energy in the electromagnetic field - the spinning wheels represented the magnetic field and the strain in the elastic bands represented the electric field; the electrical displacement running from regions of negative to positive strain. Regions with no bands were perfect conductors. The model could be used to illustrate the discharge of a capacitor, and visualise the resulting flow of energy. Electromagnetic waves were represented by oscillations of the wheels, accompanied by periodic stretching and contraction of the rubber bands to represent the oscillating orthogonal magnetic and electric fields. This representation of the ether was in some sense exact, at least in two-dimensions because the equations representing the enegy of the model were the same as those following from Maxwell's theory. There was a common Hamitonian. One could reason from the model to the theory, and thither to real electromagnetic phenomena.
FitzGerald took his model seriously. It marked the "high baroque stage of the British model-building tradition". But he did not mistake the model for a true likeness of the all-prevading ether. It was an analogy, and to mistake it for the real thing would be
"As bad a mistake as to suppose a sphere is at all like x2 + y2 + z2 = r2, and to think that it must in consequence be made of paper and ink..... "
The value of analogy was to relate the abstruse to the familar;
"If the forms of energy were as familiar a conception as eggs and money, people would find it as easy to reason about its transformation as they are about the number of eggs the old woman brought to market and sold a dozen at 3 a penny, and so forth."
The ether was practically imperceptible. FitzGerald estimated its specific heat in 1885 and found it to be immeasurably small. But it had a reality to the Maxwellians which we can hardly grasp. They believed that we are immersed in a medium in intense spinning motion, the equal counterpart of matter, and a manifestation of the omnipresence of God. No wonder those who had grown up with the ether and struggled to understand it were so loathe to abandon it! FitzGerald's splendid toy was shipped to Nurnberg in 1892 at the expense of the Bavarian government to feature in an exhibition of models and instruments used in pure and applied mathematics. Around 1970 it was tossed onto a skip outside the Physics Department by a nameless ignoramus who had no idea what it meant.
The Maxwellians, FitzGerald's inner circle of scientific colleagues, were a varied bunch united by copious correspondence and passion for their science. There was the close friend with a chair in Liverpool who enjoyed as high a reputation as FitzGerald himself as an electromagnetic experimenter and whose patent for tuning radio receivers was bought up by Marconi (Oliver Lodge, addressed by FitzGerald in letters as "My dear L", sometimes ending "with best regards to Mrs L and the little l s." FitzGerald was m d F.). There was the "thin-skinned, fatless man" who worked briefly for the Anglo-Danish Telegraph Company in Newcastle before moving in with relatives in Kentish Town and later in Paignton to lead a precarious life as as unemployed contributer of occasional articles to the Electrician, but giving us "Maxwell's" four equations in vector notation in the form we all use them today (Olivier Heaviside). Then there was the young and modestly ambitious German student of Helmholtz, making his way to his first Chair in Karlsruhe where he discovered radio waves and described their properties (Henrich Hertz) and finally the dyed-in-the-wool old Unionist, Professor in Galway and then in Cambridge who as member of parliament lamented being whipped into voting to abolish the red flag running ahead of horseless carriages, but who had brilliant insight into the workings of the ether and the Earth's magnetic field, and painstakingly edited FitzGerald's collected scientific works after his death (Joseph Larmor). This group corresponded at length on electomagnetic theory and practice, availing of the marvellous postal service of the day. Much of FitzGerald's correspondence is extant, thousands of letters in scripts ranging from Hertz's copybook copperplate to Lodge's clumps of scrawl. Dennis Weaire and David Attis plan to publish it. Without the handwriting, scholars of the e-mail generation will know much less about us than we can know of our predecessors.
But FitzGerald's scientific influence and achievement was by no means restricted to electromagnetism. His interests were wide. They spanned radioactivity, electrolysis, neurology, turbulence, flight, sunspots comets and foam. He was concerned with an astonishingly broad range of activities from the design of electric motors for public transport to repairing X-ray generators to improving the quality of butter and rearing silkworms. He was not only a physicist, but very much an engineer and also a mathematician. The notion that the science practiced in Ireland in the latter part of the 19th century, at least at Trinity, was essentially a cultural rather than a practical pursuit, is simply fatuous.
FitzGerald had a quick mind, a love of ideas and a fine instinctive grasp of physical reality. He was ever concerned that scientific discourse should be clear and intelligible, as much for the benefit of students as the practitioners themselves. Meaningless definitions earned his contempt.
"When a student is told, as an explanation of the term mass that it means the quantity of matter there in an appeal made from the obscure to the more obscure. It is a case of huggermugger. He is demoaralized by having to swallow a term of which neither he nor his teacher has a distinct idea, and he naturally concludes that the whole subject is one which no fellow can understand."
Fitzgerald's disliked imperial units, and tried to clear up the mess of units in magnetism which is still with us today. Like his uncle, he devised a consistent terminology, based on the model conduction (the phenomenon), conductance (property of a body) conductivity (intrinsic property of a material), it failed to catch on.
Though a skilled mathematician, he only ever regarded the mathematics as a tool or language of description. Let me offer you one example of his approach. At the 1897 meeting of the BA, held in Toronto, Lodge raised the question of whether you should expect spectral lines to be doubled by a magnetic field, or simply broadened. Lodge took the boat home to Liverpool straight after the meeting, but FitzGerald availed of a delightful post-conference trip laid on by the Dominion government to take delegates by special train across the praries to the Rockies and British Columbia. There he had time to think about Lodge's paper, but came to the opposite conclusion, namely that the lines should be doubled (the Zeeman effect), not broadened even though every orientation between the orbits and the direction of the magnetic field was possible. He explained his idea in a letter to Nature on 16th September.
"The motions, being assumed simply periodic in the undisturbed motion, can be resolved for each electron into three linear vibrations, two at right angles to the magnetic force and one parallel to it.. The latter is undisturbed and gives no light in the direction of the magnetic force. Each of the other linear vibrations is disturbed, and we can easily understand how by considering that a linear vibration may be considered as due to two circularly-polarized vibrations. Each of these component circular vibrations will be altered by the magnetic force normal to its plane, one being simply accelerated, the other retarded. We can consequently see that this ... leads to the conclusion that the lines would be doubled, not widened... There is no difficulty writing down the equations of the resulting motion of the electron; but it seems hardly necessary to do so, as this geometrical analysis leads to the kind of vibration emitted, which is all that we can observe."
- Introduction
- Scientific Background and Achievements
- Other Achievements
- Character and Views
- Epilogue
Last updated: Oct 06 2006. | back to top